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April 21, 2006

High Blood Pressure Tied to Hot Weather in Infancy

by Sam Savage

NEW YORK (Reuters Health) - People who were born during hot, dry years seem to have higher blood pressures, a study in the American Journal of Epidemiology indicates.

The link could be the occurrence of dehydration in infancy. "Animal studies suggest that severe dehydration in infancy results in greater sodium retention and a taste for salty foods throughout life," Dr. Debbie A. Lawlor, of the University of Bristol, UK, and colleagues explain.

This effect may be a result of "natural selection over generations produced by the survival advantage associated with the ability to retain sodium and hence water in the face of severe dehydration." However, in contemporary life, the retention of sodium in response to environmental conditions may have a down side, such as elevated blood pressure.

To investigate the link between climate conditions in infancy and adult blood pressure, Lawlor's group evaluated 3964 randomly selected UK women born in the early 20th century.

The researchers found that those who experienced the hottest and driest summers in the first year of life were more likely to have suffered severe infant diarrhea and dehydration than those who experienced cooler and wetter summers.

Also, a high average summer temperature in the first year of life correlated with a higher systolic blood pressure (the upper reading) in adulthood. Conversely, higher average summer rainfall was linked to a lower adult systolic blood pressure.

"If established, our hypothesis would have important public health implications," Lawlor's team concludes, by "highlighting the importance of avoiding dehydration in infancy not just for short-term health improvement but also for benefits to long-term cardiovascular health."